(;
AB[nr][sq][oq][mq][lq][rp][pp][op][ro][po][qn]
AW[rr][pr][or][rq][pq][nq][qp]
C[White plays.

Source:
    Maeda's Tsumego, Vol. 3]
PL[W]
(;
W[sr]
C[Pushing to the edge here seems to be the only hope for creating eye-space, but ...];
B[os]
(;
W[rs];B[qq]
C[... Black easily creates a false eye out of the remaining space.];
W[ps];B[qr];W[ns];B[mr];W[qs];B[qq]
C[Too many false eyes.]
)
    (;
    W[qq]
    C[Also doesn't work.];
    B[qs];W[rs];B[ps];W[qr];B[ns]
    C[White dies.]
    )
)
    (;
    W[ns]
    C[The only move!  But why this move is important isn't obvious.];
    B[mr];W[sr]
    (;
    B[os];W[qq];B[qs];W[rs]
    TR[ns]
    C[With the help of the marked stone, White catches Black in a liberty shortage.]
    )
        (;
        B[qq]
        C[Black can try to ruin the eye-space from this direction, but ...];
        W[os];B[qs];W[rs]
        TR[qp]
        C[... with the help of the marked stone, White catches Black in a liberty shortage in a different direction.]
        )
    )
)

